I'm not up to all the jargon but it could be the "Sympathetic" part of RSD. I bet Michael knows. I've had two root canals and both after a temporary filling was applied exploded in huge amount of pain. Puss built up to the point it was a pressure cooker. I actually (advice of dentist, 2am in the morning) yanked the filling out myself. Nothing killed the pain before hand but when I pulled the plug on that filling----Presto, total bliss.